What are some good free iPhone app games?

I like simulation games mostly but am open to any suggestions. Right now I have iLand which I really like. It's a farming game similar to FarmVille (according to my mom, I've never played it myself) but I've tried similar ones that I don't like as much due to waiting and lack of storage (in the game). I just installed a zoo game - I forget the name - and I'll give that a shot but looking for suggestions on any other good games/apps to use when I'm bored as hell, which is all the time, lol. Like I said I'm open to whatever but I mentioned the one(s) I have to give you a rough idea of what I like most. I like anything to do with animals, farming, and real life, but if you have suggestions that are completely different I won't mind. I prefer free apps without advertisements and ones that won't cost me later. I also like something somewhat simple as I have a hard time developing good techniques and poor comprehension skills. You could just tell me ones you personally like if you wish.

Hearthstone.